[llvm-bugs] [Bug 50674] New: wrong code at -O1 and above on x86_64-linux-gnu

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50674

            Bug ID: 50674
           Summary: wrong code at -O1 and above on x86_64-linux-gnu
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: zhendong.su at inf.ethz.ch
                CC: llvm-bugs at lists.llvm.org

[509] % clangtk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
632cbcac79065a62a306dbda7b3a6e1f315e3260)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /local/suz-local/opfuzz/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
[510] % 
[510] % clangtk -O0 small.c; ./a.out
[511] % 
[511] % clangtk -O1 small.c
[512] % ./a.out
Floating point exception
[513] % 
[513] % cat small.c
int a, b, f = 0;
long d = 2;
unsigned e = 1;
int main() {
  long j = a;
  int k = e / (- 1);
  if (e) {
    j = d;
    d = ~((a | e) / ~k - j - ~a);
    b = ~(~(1 | ~(d - a)) | (-200000000L - b));
    a = ~(j - ~a);
  }
  if (b < 2)
    goto L2;
  f = 1;
L1:
L2:
  a = 2 / a;
  if (f < 1)
    goto L1;
  return 0;
}

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